Figure 2.

The topology of the UDG superfamily core fold, with the conserved and unique features of different families. The core secondary-structure elements of the UDG fold are colored as in Figure 1 and numbered according to their order in the sequence. The elements observed only in the MUGs are shown in gray. The conserved motif I occurs after strand 1 and motif II occurs after strand 4 and forms the active-site pocket in the three-dimensional structure.